Why User Cannot Access Mailbox in Exchange 2016/13/10?

The most common issue around Exchange User arise when they Can't Access mailbox Created with Exchange 2016/13/10 or below version. While accessing the Mail and other details via Outlook and OWA (Outlook Web App). 

Why User Cannot Access Mailbox In  Exchange 2010/2013/2016

1.  Mostly Error interrupts users from accessing their mailboxes either via OWA and ActiveSync, only if the Exchange database is totally disconnected dismounted, or database is separated from the Exchange server. Well, it is a common error message for Exchange users and there may several causes for this issue such as Exchange database corruption, Exchange database is disconnected and so forth. 
2. Even when the Directory Service Access (DSAccess) tries to find the disconnected mailbox in the Active Directory, it returns the same error. If the GUID of mailbox contains the client-side cache and after that user tries to connect with server database yet, the server DB GUID cache has been updated. It disconnects the Exchange Database and results in DatabaseGUIDNotFound Error.

Case 1: Cannot login after the mailbox is disabled and attached to different AD user account

Sometimes while renaming the Exchange account due to some reasons like changed surname or username, users disable the Exchange mailbox to clean the databases. It makes mailboxes visible in Detached Mailboxes folder. Following Exchange Management Shell command is utilized for the same: get-mailboxdatabase | clean-mailboxdatabase

After this, if a user deletes the AD user account and creates a new AD user account then, connect the Detached mailbox to new AD user account, the user gets new login credentials. It is the point where problem occurs. Because then, users could not log in to their account and OWA also says that the account was disabled and displays following error message:

Exception type: Microsoft.Exchange.Data.Storage.AccountDisabledException

To rectify this issue first, check the AD account and make sure it is not disabled. Then, force an AD Replication and disable the account, replicate the AD. Still, if you cannot log in to OWA, run below command:   get-mailboxdatabase | clean-mailboxdatabase

After this, one can easily login to OWA and Outlook account to view details their mailboxes.

Note: Sometimes account not accessed due to corruption in Exchange Database and to Repair Exchange Database, you can for manual or automated solution

Case 2: Cannot Access Mailbox After Migrating Exchange to Office 365 Account

Various scenarios occur where Exchange users face problem in accessing Exchange mailbox after exporting mailbox into a  managed environment from Microsoft Exchange Server source. If there is an issue with the configuration of user mailbox, then check, local profile or Autodiscover service it restricts users from accessing their mailbox after migration.

If you are running Microsoft Outlook 2010 or Microsoft Office Outlook 2007, you can check the main cause of error either it is the configuration of the mailbox or Autodiscover service. Determine that the source object is configured properly or not. 

Solution to Access Mailbox in Exchange 2010/2013/2016

Check Primary Simple Mail Transfer Protocol (SMTP) Address: Primary SMTP address should match with the primary SMTP address in the managed environment. The managed primary SMTP address is recorded in the address book and in Active Directory schema of the managed environment. Now, review your source primary SMTP address in source Active Directory schema.

Check the Target Address: Make sure that the source object has a target address with a suffix of mgd.<CustomerDomain>.com also, a matching secondary SMTP address in the managed domain. There should no target address on the managed object. Managed secondary SMTP address will be recorded in the address book and in Active Directory schema of the managed environment. Eventually, review the source target address in source Active Directory schema.

Concluding Lines

Whenever user Can't Access their Mailbox created via Exchange 2010/13/16, then user go for the solution to fix the issues, which mostly occur due to Disconnection or Databased is dismounted or any other network or migration process.